1. Field of the Invention
The present invention relates in general to systems for driving engine accessories, such as alternator, compressor of air conditioner and the like, of an automotive internal combustion engine, and more particularly to the engine accessory driving systems of a type which includes a hydraulic pump powered by the engine and a hydraulic motor powered by the hydraulic pump for driving the engine accessories.
2. Description of the Prior Art
As is known, automotive engine accessories, such as alternator, compressor of air conditioner, and the like are usually powered by the internal combustion engine mounted on the vehicle. In some of the motor vehicles, the power transmission from the engine to the engine accessories is carried out by using transmission belts each being directly driven by a crankshaft of the engine. However, this type power transmission sometimes brings about a power lack of each engine accessory particularly when the engine is under idling operation.
In order to solve this drawback, a driving system has been proposed by, for example, Japanese Utility Model First Provisional Publication 63-79432 and Japanese Patent First Provisional Publication 2-175336, in which a hydraulic motor driven by a hydraulic pump powered by the engine is used for driving the engine accessory. That is, the hydraulic pump is driven by the crankshaft of the engine through a transmission belt, and a pressurized oil produced by the hydraulic pump is fed through a separate high pressure pipe to the hydraulic motor to operate the same.
However, due to its inherent construction, even this driving system has such a drawback that under operation of the engine, the high pressure pipe tends to vibrate due to inevitable pulsation of the highly pressurized oil discharged from the hydraulic pump, which causes increase in noise level of the engine. Furthermore, the high pressure prevailing in the pipe causes a complicated and thus expensive construction of seal at both ends of the pipe. Furthermore, assembly of the pipe around the engine is troublesome.